1. Field of the Invention
The present invention relates to an image forming apparatus using an electrophotographic system or electrostatic recording system, particularly to an image forming apparatus for a copying machine, a printer, a facsimile machine, or a complex machine having the functions of these devices.
2. Related Background Art
A full-color-image forming apparatus using an electrophotographic system is hitherto proposed which makes it possible to sequentially execute developing operations by selectively rotating a desired developing apparatus to a developing position by a developing rotary unit mounting a plurality of corresponding toner cartridges (toner containers) together with a plurality of developing apparatuses.
The above image forming apparatus is constituted so as to remove a toner cartridge with no toner among a plurality of toner cartridges from the developing rotary unit and replace it with a new one.
However, when a plurality of toner cartridges runs short of toner or decreases in toner at the same time, a technique is needed which allows a user to replace toner cartridges without confusion of the user by considering the replaceability or usability of the a toner container.